Double an infinitely long number
You are given a real number as an endless stream of digits. Output twice of it in an endless stream of digits.
The exact format is flexible. You may separate digits and the two parts of the number by any reasonable separator, or without separators, as long as it...

This wasn't originally intended for code-golf, just as a little debugging routine to roughly visualize something "goofy" going on in a model of some (irrelevant here) physical process. But when I saw how surprisingly short it was, compared to my expectations, I just wondered if it can be further ...

Count the length of head movement
code-golf parsing pathfinding
Once upon a time I wanted to order custom tokens for a board game. They say they can do it, and then they present me their price list. I was confused because they charge per inch of head movement.
INPUT: a 2d grid:
|,-,\,/ are s...

This challenge was prety interesting for me. You can use any language. Shortest time on max conditions = win. Enjoy!
Designer Arseny wants to draw a new brilliant logo. For a special conceptuality, Arseny decided that he would use a special stamp for his drawing. A stamp is a rectangle (h×w), ea...

CMC: Implement a "strange algorithm" for computing e. The precision doesn't need to be good, results between 2.70 and 2.75 are acceptable, and the result does not need to be deterministic. (Provided that, in theory, the result would approach e under certain circumstances)

Part 1 of the task is here
Flags Mashup Bot is a small Twitter bot that generates a new country name based on two random country names and tweets the result every couple of minutes.
Task
Your task is to replicate what the bot does by writing a script or a function based on the following crite...

@Adám I have an APL question or two. 1) how can I get the N'th element from an array? 2) If I have an array of unknown length, how can I reshape it into a matrix with two rows? (I know one way would be to calculate half the length of the array and use that as an argument to rho, I'm just wondering if there's an easier way)

@Mr.Xcoder Generate N random numbers uniformly distributed on the interval (0,1). Compute their consecutive differences. The fraction of those differences that are less than 1/N converges to 1-1/e (in probability) as N increases. Code. Or golfier :-)